package com.sen.Midium;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

/**
 * Given an array nums of n integers, are there elements a, b, c in nums such that a + b + c = 0?
 * Find all unique triplets in the array which gives the sum of zero.
 *
 * Note:
 *
 * The solution set must not contain duplicate triplets.
 *
 * Example:
 *
 * Given array nums = [-1, 0, 1, 2, -1, -4],
 *
 * A solution set is:
 * [
 *   [-1, 0, 1],
 *   [-1, -1, 2]
 * ]
 */

public class L015_3Sum {
    public List<List<Integer>> threeSum(int[] nums) {

        Arrays.sort(nums);
        List<List<Integer>> res = new ArrayList<>();
        for(int i = 0; i < nums.length - 2; i++){
            if(i > 0 && nums[i] == nums[i - 1]) continue;
            int left = i + 1;
            int right = nums.length - 1;

            while(left < right){
                int sum = nums[i] + nums[left] + nums[right];
                if(sum == 0){
                    res.add(Arrays.asList(nums[i], nums[left], nums[right]));
                    while(left < right && nums[left] == nums[left + 1]){
                        left++;
                    }
                    while(left < right && nums[right] == nums[right - 1]){
                        right--;
                    }
                    left++;
                    right--;
                }else if(sum > 0){
                    right--;
                }else if(sum < 0){
                    left++;
                }
            }
        }

        return res;
    }
}
